Vehicles are equipped with various types of communication systems that provide or facilitate various types of functions. For instance, a vehicle may be equipped with a global positioning satellite (GPS) system that provides for locating the vehicle and providing information concerning the location of the vehicle to a user. Vehicle security systems are also employed in many vehicles to protect the vehicle and its contents from theft or other criminal activity. For example, a vehicular security system may be configured to communicate with some outside entity (e.g., a police or security center) and when an attempt is made to break into a vehicle, the vehicular security system may transmit messages to the outside entity where appropriate action may be taken to prevent or stop the break in. Some jurisdictions even require the use of security systems in vehicles because of the high number of vehicle break-ins or thefts in these areas.
If a vehicle is stolen, stolen vehicle tracking (SVT) applications attempt to track and sometimes recover the stolen vehicle. To give one example, some SVT applications rely upon a GPS system to pinpoint the location of the vehicle and a Global System for Mobile communications (GSM) cellular network to report the incident to a service provider via Short Message Service (SMS) or General Packet Radio Service (GPRS) data connections.
Potential thieves have sometimes attempted to jam the receiver hardware located at the vehicle by employing devices that create a strong wide-band signal in the receive band and thereby block the GPS satellite from being received at the vehicle and/or to block GSM network signals that are sent from the cellular base station to the vehicle.
During normal operation, a transceiver (e.g., a GSM transceiver) receives frequency correction information from the base station and makes necessary adjustments to its time base to compensate for any frequency error between the transceiver and the network. However, if the transceiver is jammed, the transceiver's transmit frequencies will drift, the compensation will not be performed at the transceiver, and the transceiver will broadcast at new, drifted-to frequencies that are not monitored by the base station. Consequently, any warning messages sent by the transponder at the vehicle indicating that the vehicle is stolen will not reach the base station (since they will be broadcast on frequencies not monitored by the base station) and appropriate action will not be taken.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and/or relative positioning of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention. It will further be appreciated that certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required. It will also be understood that the terms and expressions used herein have the ordinary meaning as is accorded to such terms and expressions with respect to their corresponding respective areas of inquiry and study except where specific meanings have otherwise been set forth herein.